Vulnerability-Lookup

FKIE_CVE-2021-47515

Vulnerability from fkie_nvd - Published: 2024-05-24 15:15 - Updated: 2026-08-04 10:17

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: seg6: fix the iif in the IPv6 socket control block When an IPv4 packet is received, the ip_rcv_core(...) sets the receiving interface index into the IPv4 socket control block (v5.16-rc4, net/ipv4/ip_input.c line 510): IPCB(skb)->iif = skb->skb_iif; If that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH header, the seg6_do_srh_encap(...) performs the required encapsulation. In this case, the seg6_do_srh_encap function clears the IPv6 socket control block (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163): memset(IP6CB(skb), 0, sizeof(*IP6CB(skb))); The memset(...) was introduced in commit ef489749aae5 ("ipv6: sr: clear IP6CB(skb) on SRH ip4ip6 encapsulation") a long time ago (2019-01-29). Since the IPv6 socket control block and the IPv4 socket control block share the same memory area (skb->cb), the receiving interface index info is lost (IP6CB(skb)->iif is set to zero). As a side effect, that condition triggers a NULL pointer dereference if commit 0857d6f8c759 ("ipv6: When forwarding count rx stats on the orig netdev") is applied. To fix that issue, we set the IP6CB(skb)->iif with the index of the receiving interface once again.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/6431e71093f3da586a00c6d931481ffb0dc2db0e	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/666521b3852d2b2f52d570f9122b1e4b50d96831	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/ae68d93354e5bf5191ee673982251864ea24dd5c	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/b16d412e5f79734033df04e97d7ea2f50a8e9fe3	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/ef8804e47c0a44ae106ead1740408af5ea6c6ee9	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/6431e71093f3da586a00c6d931481ffb0dc2db0e	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/666521b3852d2b2f52d570f9122b1e4b50d96831	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/ae68d93354e5bf5191ee673982251864ea24dd5c	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/b16d412e5f79734033df04e97d7ea2f50a8e9fe3	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/ef8804e47c0a44ae106ead1740408af5ea6c6ee9	Patch

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	5.0
linux	linux_kernel	5.0
linux	linux_kernel	5.0
linux	linux_kernel	5.0
linux	linux_kernel	5.16
linux	linux_kernel	5.16
linux	linux_kernel	5.16
linux	linux_kernel	5.16

JSON

To clipboard

{
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          "vendor": "Linux",
          "versions": [
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              "version": "5.0"
            },
            {
              "lessThan": "5.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "4.14.*",
              "status": "unaffected",
              "version": "4.14.258",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "4.19.*",
              "status": "unaffected",
              "version": "4.19.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.4.*",
              "status": "unaffected",
              "version": "5.4.165",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.85",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "5.16",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
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    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nseg6: fix the iif in the IPv6 socket control block\n\nWhen an IPv4 packet is received, the ip_rcv_core(...) sets the receiving\ninterface index into the IPv4 socket control block (v5.16-rc4,\nnet/ipv4/ip_input.c line 510):\n\n    IPCB(skb)-\u003eiif = skb-\u003eskb_iif;\n\nIf that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH\nheader, the seg6_do_srh_encap(...) performs the required encapsulation.\nIn this case, the seg6_do_srh_encap function clears the IPv6 socket control\nblock (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163):\n\n    memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));\n\nThe memset(...) was introduced in commit ef489749aae5 (\"ipv6: sr: clear\nIP6CB(skb) on SRH ip4ip6 encapsulation\") a long time ago (2019-01-29).\n\nSince the IPv6 socket control block and the IPv4 socket control block share\nthe same memory area (skb-\u003ecb), the receiving interface index info is lost\n(IP6CB(skb)-\u003eiif is set to zero).\n\nAs a side effect, that condition triggers a NULL pointer dereference if\ncommit 0857d6f8c759 (\"ipv6: When forwarding count rx stats on the orig\nnetdev\") is applied.\n\nTo fix that issue, we set the IP6CB(skb)-\u003eiif with the index of the\nreceiving interface once again."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: seg6: corrige el iif en el bloque de control del socket IPv6 Cuando se recibe un paquete IPv4, ip_rcv_core(...) establece el \u00edndice de la interfaz de recepci\u00f3n en el bloque de control del socket IPv4 (v5 .16-rc4, net/ipv4/ip_input.c l\u00ednea 510): IPCB(skb)-\u0026gt;iif = skb-\u0026gt;skb_iif; Si ese paquete IPv4 debe encapsularse en un encabezado IPv6+SRH externo, seg6_do_srh_encap(...) realiza la encapsulaci\u00f3n requerida. En este caso, la funci\u00f3n seg6_do_srh_encap borra el bloque de control del socket IPv6 (v5.16-rc4 net/ipv6/seg6_iptunnel.c l\u00ednea 163): memset(IP6CB(skb), 0, sizeof(*IP6CB(skb))); El memset(...) se introdujo en El commit ef489749aae5 (\"ipv6: sr: clear IP6CB(skb) en la encapsulaci\u00f3n SRH ip4ip6\") hace mucho tiempo (29 de enero de 2019). Dado que el bloque de control del socket IPv6 y el bloque de control del socket IPv4 comparten la misma \u00e1rea de memoria (skb-\u0026gt;cb), la informaci\u00f3n del \u00edndice de la interfaz de recepci\u00f3n se pierde (IP6CB(skb)-\u0026gt;iif se establece en cero). Como efecto secundario, esa condici\u00f3n desencadena una desreferencia del puntero NULL si se aplica el commit 0857d6f8c759 (\"ipv6: al reenviar estad\u00edsticas de recuento de rx en el netdev original\"). Para solucionar ese problema, configuramos IP6CB(skb)-\u0026gt;iif con el \u00edndice de la interfaz de recepci\u00f3n una vez m\u00e1s."
    }
  ],
  "id": "CVE-2021-47515",
  "lastModified": "2026-08-04T10:17:06.950",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2021-47515",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2024-09-10T15:35:33.340330Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2024-05-24T15:15:12.937",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/6431e71093f3da586a00c6d931481ffb0dc2db0e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/666521b3852d2b2f52d570f9122b1e4b50d96831"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "url": "https://git.kernel.org/stable/c/ae68d93354e5bf5191ee673982251864ea24dd5c"
    },
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/b16d412e5f79734033df04e97d7ea2f50a8e9fe3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
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      "url": "https://git.kernel.org/stable/c/ef8804e47c0a44ae106ead1740408af5ea6c6ee9"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/6431e71093f3da586a00c6d931481ffb0dc2db0e"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
        "Patch"
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      "url": "https://git.kernel.org/stable/c/666521b3852d2b2f52d570f9122b1e4b50d96831"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
        "Patch"
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      "url": "https://git.kernel.org/stable/c/98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1"
    },
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      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
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      "url": "https://git.kernel.org/stable/c/ae68d93354e5bf5191ee673982251864ea24dd5c"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/b16d412e5f79734033df04e97d7ea2f50a8e9fe3"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/ef8804e47c0a44ae106ead1740408af5ea6c6ee9"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-476"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}

CVE-2021-47515 (GCVE-0-2021-47515)

Vulnerability from cvelistv5 – Published: 2024-05-24 15:09 – Updated: 2026-08-05 08:48

Title

seg6: fix the iif in the IPv6 socket control block

Summary

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2024-09-10 15:35 UTC

Assigner

Linux mitre root

References

6 references

URL	Tags
https://git.kernel.org/stable/c/b16d412e5f7973403…
https://git.kernel.org/stable/c/6431e71093f3da586…
https://git.kernel.org/stable/c/ef8804e47c0a44ae1…
https://git.kernel.org/stable/c/666521b3852d2b2f5…
https://git.kernel.org/stable/c/98adb2bbfa407c929…
https://git.kernel.org/stable/c/ae68d93354e5bf519…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: c630ec8bdadae9d557b1ceb9d6c06e149108a0d4 , < b16d412e5f79734033df04e97d7ea2f50a8e9fe3 (git) Affected: 2f704348c93ff8119e642dae6a72327f90b82810 , < 6431e71093f3da586a00c6d931481ffb0dc2db0e (git) Affected: ef489749aae508e6f17886775c075f12ff919fb1 , < ef8804e47c0a44ae106ead1740408af5ea6c6ee9 (git) Affected: ef489749aae508e6f17886775c075f12ff919fb1 , < 666521b3852d2b2f52d570f9122b1e4b50d96831 (git) Affected: ef489749aae508e6f17886775c075f12ff919fb1 , < 98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1 (git) Affected: ef489749aae508e6f17886775c075f12ff919fb1 , < ae68d93354e5bf5191ee673982251864ea24dd5c (git) Affected: b71b7e0280f47b4ac633fbfd153423814ea87810 (git) Affected: 4.14.98 , < 4.14.258 (semver) Affected: 4.19.20 , < 4.19.221 (semver) Affected: 4.20.7 , < 4.21 (semver)
Linux	Linux	Affected: 5.0 Unaffected: 0 , < 5.0 (semver) Unaffected: 4.14.258 , ≤ 4.14.* (semver) Unaffected: 4.19.221 , ≤ 4.19.* (semver) Unaffected: 5.4.165 , ≤ 5.4.* (semver) Unaffected: 5.10.85 , ≤ 5.10.* (semver) Unaffected: 5.15.8 , ≤ 5.15.* (semver) Unaffected: 5.16 , ≤ * (original_commit_for_fix)

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          "product": "Linux",
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          "vendor": "Linux",
          "versions": [
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              "value": "AV:N - On an SRv6 PE/router with ip4ip6 encap routes, a remote IPv4 packet is received, encapsulated in seg6_do_srh_encap(), then forwarded via ip6_forward(), so the crash is reachable over the network without local access.\nAC:L - Once SRv6 encap for IPv4 is configured (the intended deployment for this code), any matching IPv4 packet reliably clears IP6CB(skb)-\u003eiif and hits the NULL dereference; no race or attacker-uncontrollable memory layout is required.\nPR:N - Triggering requires only sending unauthenticated IPv4 packets that match an already-configured SRv6 encap route; the attacker needs no account or capability on the target.\nUI:N - Packet processing runs entirely in the kernel receive/forward path with no victim user action beyond the router already having SRv6 encap configured.\nS:U - The NULL dereference oopses the same host kernel that performs forwarding and does not cross a VM, IOMMU, or other security-authority boundary.\nC:N - This is a pure NULL pointer dereference of idev in ip6_forward() after iif is cleared to zero, with no OOB read, UAF, or other information-disclosure primitive.\nI:N - The fault is a straight NULL dereference of idev-\u003ecnf.disable_policy with no write primitive, type confusion, or memory corruption that could alter kernel state or hijack control flow.\nA:H - Dereferencing the NULL inet6_dev pointer in ip6_forward() causes a kernel oops/panic and can be re-triggered at will by remote packets, taking down the system."
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    "assignerShortName": "Linux",
    "cveId": "CVE-2021-47515",
    "datePublished": "2024-05-24T15:09:29.334Z",
    "dateReserved": "2024-05-24T15:02:54.824Z",
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.